Method of producing rayon filaments from viscose



Dec. 20, 1949 P. H. scHLossER ETAL 2,491,937

METHOD OF PRODUCING RAYON FILAMENTS FROM VISCQSE Filed Sept. 12, 1944 2Sheets-Sheet 1 INVENTOR.

Haul Henry Sch user BY Wad Logan Mfckel/ M Q 7 7mm! 894M4 6 ATTORNEY.

Dec. 20, 1949 P. H. SCHLOSSER ET AL 2,491,937

METHOD OF PRODUCING RAYON FILAMENTS FROM VISCOSE 2 Sheets-Sheet 2 FiledSept. 12, 1944 asoas z y a ,Maaza asv n ag lNVENTORS Paul H Sc/zlosserPeg? L. Mz'tcfiel/ ATTORNEYS Patented Dec. 20, 1949 METHOD OF PRODUCINGRAYON FILAMENTS FROM VISCOSE Paul Henry Schlosser and Shelton, Wash.,

Reid Logan Mitchell,

asslgncrs to Rayonier Incorporated, Shelton, Wash a corporation ofDelaware Application September 12, 1944, Serial No. 553,734

15 Claims.

This invention relates to viscose production and has for its object theprovision of an improved method of producing spun filaments and thelike. More particularly, the invention provides an improved method ofproducing crinkled or potentially crinkled regenerated cellulosicfilaments of viscose origin.

The method of the invention, in its broad aspect, is characterized byspinning a viscose solution of special composition and subjecting theextruded filaments to high tension stretching during the operation ofcoagulation and regeneration. The resulting regenerated and stretchedcellulosic filaments have the capacity to crinkle spontaneously whentreated with water under conditions permitting free shrinkage. Themethod of the invention not only provides a method of producingfilaments having the capacity to crinkle but also a method of crinklingthe filaments. The special viscose solution used in the practice of theinvention is relatively high in both the cellulose and the caustic sodacontents and is spun in an acid spin bath and is stretched during theoperation of coagulation and regeneration. Coagulation and regenerationare preferably carried out with a normal Muller bath such as is commonlyused with normal composition viscoses in spinning ordinary non-crinkledyarns.

In addition to the viscose composition, which will be fully describedhereinafter, another important aspect of the method of the invention isthe stretching of the filaments during coagulation and regeneration andthe control of the chemical state and the physical conditions inconsequence of which the regenerated filaments possess the property ofcrinkling spontaneously when treated with water under conditionspermitting free shrinkage. The stretched filaments may be prevented fromshrinking by mechanical stress and subsequently washed and dried whilestill under stress. The dry filament produced in this manner will bestraight with no apparent crinkle but will nevertheless retain itscapacity to crinkle as will be evident when the filament isrewetted withwater under conditions permitting free shrinkage.

Without any intention to limit the invention by any theoreticalexplanation of the improved results obtained thereby, the following moreor less theoretical discussion is submitted largely for the purpose offacilitating an understanding of the invention in its variousmodifications:

There is evidence that the high caustic soda content of our specialviscose composition of our invention retards coagulation of the insideof the filament while the outside is being coagulated and regenerated.The high cellulose content of our special viscose tends to give a rapidformation of surface skin which is more' dense than with normal viscoseand less easily penetrated by the acid bath. Therefore, two layers areformed of such difference in initial structure that when stress isimposed on the filament, as by stretching while still in a semi-plasticcondition, the inside portion is stretched with relatively littleincrease in uniaxial orientation, while the outside portion becomeshighly oriented along the filament axis by the stretching. As a result,unbalanced potential strains then exist between the inside and theoutside portions; the oriented portion having a greater tendency toshrink than the unoriented portion. If the filament is now allowed toshrink in water (shrinking takes place along the filament axis, swellingacross the axis), these strains assert themselves and are manifest in acrinkled form. This crinkled form, in which the strains are equalized,then represents the normal and stable state of the filament, whereas thestraight form represents the unstable state. Again the straight, thoughunstable, form can exist both in the dry and wet condition of the yarn,but when wet, presence of certain salts in high concentration or theaction of mechanical force is required to prevent spontaneous shrinkageand crinkling. Due to this structural origin, this type of crinkle isvery permanent, and due to the residual uniaxial orientation, thetensile strength is high.

In carrying out a method of the invention, it is necessary to use aviscose solution of special composition. The special composition viscoseof this invention has a cellulose content of from 9% to 13%, and acaustic soda content of from 8% to 13%, with a cellulose to caustic sodaratio of from 0.833 to 1.13. Under the most favorable conditions, aviscose containing about 10% each of cellulose and caustic soda givesthe most effective crinkling. However, compositions close to this, suchas 10 to 9, 10 to 11, 9 to 9, 9 to 10, and 11 to 11 of cellulose andcaustic soda, respectively,

' 9% cellulose, caustic soda 9% cellulose, 10.8% caustic soda 10%cellulose, 12% caustic soda 13% cellulose, 13% caustic soda 10%cellulose. 8.9% caustic soda Under the preferred conditions asexemplified by a viscose having a cellulose content of 10% and a causticsoda content of 10%, the ratio of cellulose to caustic soda is 1.0. Thisalso is the preferred ratio for any of the other cellulose values whichhave been found to be workable, namely, 9% to 13%. This preferred ratioof 1.0 becomes the more critical the more the value of 13% celluloseconcentration is approached. In other words, the greatest leeway in thechoice oi the cellulose to caustic soda ratio within the restrictedratio range of 1.13 to 0.833 is aflorded at cellulose concentrations ofnot over 10% where the whole range is efiective. But as the extreme highcellulose concentration of 13% is approached, the ratio of caustic sodato cellulose narrows down to the preferred value of 1.0.

The conditions which must be observed in the practice of the inventionare somewhat critical. Slight variations in viscose composition, in spinbath composition, in bath temperature, in spinning tension and filamentdenier all affect the crinkle. Satisfactory crinkling depends not onlyupon the composition of the viscose but upon the maintenance of aparticular state during coagulation and regeneration, and in particularthe application of a considerable degree of stretch to the yarn duringspinning.

In accordance with this aspect of the inventlon, a viscose solutionhaving the special composition previously described is extruded into aregenerating bath of the normal Muller type, and, while the cellulose isundergoing coagulation, the filaments are subjected to high tensionstretching. The term "high tension stretching, as used herein, refers totensions, during the operation of coagulation and regeneration, about0.5 gm. per denier and especially to tensions of 0.75 to 1.0 gm. perdenier or higher. Actually the upper limit in high tension spinning isthe point where damage to the filaments is noticed-either throughvisible breakage, evidenced by sticking of filaments on godets or rollerguides, or through noticeably poorer physical properties of the finishedyarn. After regeneration and after or during washing free from spin-bathsolution, the wet stretched filaments have the capacity to crinkle whenfree shrinkage is permitted. The filaments may be subjected to the usualaftertreatments such as washing, desuli'urizing, drying and the like,but when crinkling is to be avoided to make a product having thecapacity to crinkle, the stretched filaments are prevented fromshrinking while in a wet state. For example, the filaments may be washedand dried in package form on a bobbin without crinkling, but if wet withwater while free to contract, they crinkle spontaneously.

The special viscose is extruded into or otherwise suitably contactedwith a regenerating medium. e. g., in a normal Muller spin bath. Anormal Muller spin bath, as referred to herein, is a spin bath in whichsulfuric acid and sodium sulfate are present in such proportions thatthe bath consists substantially of a solution of Hal-I804 together withsome excess NaaSOc. Such a bath may contain in addition MgBOs, glucoseand ZnSOi, the latter in amounts up to about 1.5%. As used in thisapplication, the term "nob mal Muller spin bat does not include bathscontaining iron in any appreciable quantity or zinc in amounts greaterthan 1.5%. Such special baths have ahlghly delayed coagulating action,and while sometimes used for stretch spinning. nevertheless, are not ofthe character used in this invention. The bath is preferably used at atemperature within the range of 45 C. to 55 0. However, some deviationsfrom these upper and lower limits are permissible.

The viscose may have a salt index varying from around 4.0 to 7.5, apreferred range being from 5.5 to 6.0, and especially when spinning aviscose containing about 10% each of cellulose and caustic soda. Thenewly-formed filaments are subjected to a high degree of stretching, assoon as is feasible after extrusion into the spin bath. Numerousstretch-spinning methods are applicable, a very effective one being theprogressive stretching of the filaments while in contact with theregenerating spin bath. For example, a stretching op ration such as iscommonly used in the production of high tenacity tire-cord yarn is verydesirable. striations in the filaments set up by stretching stresses arelater manifest in irregular shrinkage forces when shrinkage is inducedby treating the filaments with water, for example, by replacing thespinning bath held by the regenerated filaments with water in theprocess of the normal washing operation.

The stretched filaments may be taken directly from the spin bath, orthey may be collected in the form of an acid cake, in a centrifugal potor on a bobbin, and then reeled into skelns or cut into staples. At thisstage, the filaments are normal in appearance and straight, but whenthey are washed with water and allowed to shrink freely, crinklingoccurs immediately and spontaneously. It is notable that the crinklesare extremely prominent in the wet state and, of course, are retainedwhen in the dry state. In producing dry crinkled filaments, it isnecessary to dry the wet crinkled filaments while they are in a relaxedstate. Moreover, in addition to possessing a high degree of crinkle, theresulting filaments have unusually high tensile strength.

The invention involves the production of a straight viscose filamenthaving the capacity to crinkle spontaneously when treated with water inthe absence of chemical conditions or physical forces which inhibit freeshrinkage, such as a high concentration of certain salts that exist inthe spinning solution, or a restraining force such as results fromtightly winding the filaments on a bobbin.

In producing straight filaments having the capacity to crinkle, thefilaments are prevented from crinkling either by washing and dryingunder tension or by washing under tension and impregnating the wet yarnwith a solution which inhibits crinkling. e. g., a saturated solution ofammonium sulfate, methanol, etc. The result in either case is a straightproduct having the capaclty to crinkle when treated with water underconditions permitting shrinkage.

The simplest method of producing straight filaments with a capacity tocrinkle is to simply dry the washed filaments under tension. Anotherdesirable procedure may be to lead the washed filaments while undertension through a bath containing a saturated solution of ammoniumsulfate. I! the electrolyte of the spin bath is washed out of the yarndirectly with the ammonium sulfate solution instead of with water,tension is not needed. In any case the filaments are prevented fromcrinkling by the inhibiting action of the ammonium sulfate and can becut, opened and dropped into water, thereby crinkling spontaneously, ormay be preserved for long periods of time in the wet state as finishedfilaments having the capacity to crinkle.

A swelling bath, as for instance, 1% NaOH in water or 5% dimethyldibenzyl ammonium hydroxide in water may be particularly useful inresweiiing dried fiaments for purposes of crinkling.

Treatment of the stretched filaments with water as by washing, dipping,spraying, or the like causes the strains in the stretched filaments toassert themselves and to crinkle the filaments when under conditionspermitting free shrinkage. Wet" filaments, stretched during spinning andstill "wet" with spin bath, are usually not under conditions permittingfree shrinkage due to the presence of substantial amounts of inhibitingelectrolytes, such as soduim sulfate from the spinning solution.Treatment of such filaments with water reduces the concentration of theelectrolyte, and in the absence of a mechanical restraining force, thefilaments will crinkle. In the case of filaments washed and dried whilerestrained from shrinkage by mechanical force, treatment of the dryfilaments with water, as by simple immersion, under conditionspermitting free shrinkage, namely, in the absence of any restrainingmechanical force on the filaments, causes the filaments to crinkle. Suchshrinkage with water may be effected with fresh water or with anysuitable water solution providing the water does not contain a highconcentration of a material that inhibits crinkling such as ammoniumsulfate, sodium sulfate, or potassium fluoride. Only strong solutions ofthese salts exert sufllcient lyotropic action to prevent crinkllng-evena solution still allows good crinkling.

On the other hand as previously described, the water may containmaterials which aid crinklingas for example, small concentrations ofNaOH or dimethyl dibenzyl ammonium hydroxide or a high concentration ofK1 or KCNS.

The following are illustrative examples of the invention:

Example I Viscose with a composition of 10% cellulose, 10% NaOH andviscosity of 50 sec. (falling ball) was spun at a salt index of 5.8 intoa common Muller type spin bath (140 g./liter H2804, 245 g./liter NAzSOi,50 g./liter glucose, 12.5 g./liter ZnSO4) maintained at 47 C. using 100hole spinnerets having holes 0.0020 of an inch in diameter. Thefilaments of 200 denier (total) were stretchspun at 65 meters per minuteunder a tension of 200 g. applied to the strand soon after contactingthe bath and while immersed in the spin bath over a path of about 40inches. The filaments were collected in a centrifugal spinning pot, thenreeled off from the acid cake into a skein and placed in a water wash.The skein direct from acid cake consisted of straight filaments, asillustrated in Fig. 1, which, however, became highly crinkled, asillustrated in Fig. 2, when placed in water and allowed to shrinkfreely. The crinkled filaments were then desuliured, bleached and dried.The filaments were highly crinkled, had good hand, were bulky and ofdull lustre. The tenacity of the filaments was 2.5 g./denier dry, 1.5g./denier wet; elongation (with crinkles straightened out) equalled 18%when dry and 24% when wet. The additional elongation due to crinkles was15 to 20% for this continuous filament yarn with a twist of 3 turns perinch.

To further illustrate the invention, using the same spinning conditionsgiven in Example I, crinkles were not obtained (1) with viscose ofcomposition 7.5 cellulose and 6.5 sodium hydroxide spun under hightension of l g./denier, and (2) with viscose of composition 10%cellulose and 10% sodium hydroxide spun under low tension oi 0.25g./denier.

Example I! Viscose made from wood pulp and having the composition 9%cellulose and 9% sodium hydroxide at a sodium chloride index of 5.5 wasspun into an acid spin bath with composition 125 g./liter H2504, 235g./liter Na:S04, 12.5 g./liter ZnSOa maintained at a temperature of 47.5C. The viscose was extruded from a spinneret having 120 holes, each holebeing 0.0030 of an inch in diameter at a rate to give filaments of 400denier which were grouped and stretched by passing them over a series oftension wheels and then wound up on a bobbin at a speed of meters perminute under a tension of 350 g. The filaments were out into 2-inchstaples and in the acid-set condition were still straight as thefilaments of Fig. 1; When these straight staples were put in water, avery high crinkle developed immediately and spontaneously; the crinkledstaples then having a length of only V inch.

Example III Viscose with a composition of 10% cellulose and 9% sodiumhydroxide, a viscosity of seconds and a salt index of 6.0 was spun intoa spin bath with a composition of g./liter H2804, 245 g./liter Na2SO4,50 g./liter glucose, 12.5 g./liter ZnSO4 at 50 C. using a spinneret with60 holes.

each having a diameter of 0.0031 of an inch. The filaments of 200 denierwere grouped into a thread which was stretch-spun at 60 meters perminute under a tension of 190 g. As the thread passed through the bath,it was stretched under progressively increasing tension while immersedin the spin bath. When collected in a centrifugal pot, reeled oil into askeln and washed, the thread showed a fair degree of crinkle. Under thesame spinning conditions, a viscose composition of 10% cellulose and6.5% sodium hydroxide showed no tendency to crinkle, while a viscosehaving 10% each of cellulose and caustic soda gave excellent crinkle.

Example IV Viscose with a composition of about 10% each of cellulose andcaustic soda was spun at a salt index of 5.5 into an acid spin bath withthe composition g./liter H2504, 320 g./liter Na2SO4, 12 g. /liter ZnSOand 55 g./liter glucose at 52 C. using a spinneret with 480 holes eachhaving a diameter of 0.0030 inch. The filaments of 1100 total denierwere grouped into a thread which was drawn around a series of tensionwheels submerged in the spin bath to give a bath path of about 100inches and a tension of about 950 grams at the windup where the yarn wascollected on a bobbin at a speed of 85 meters/minute. A bobbin of the 7syarn was washed acid free and dried on the bobbin to yield straight yarnwith capacity to crinkle. When a 4-inch staple (about 4 in, x x h) ofthis dry yarn was dropped into a solution of dimethyl dibenzyl ammoniumhydroxide in water, it crinkled immediately and spontaneously yielded ahighly crinkled bulky chip only 1 inch in length and approximately /2in. wide and V4 in. thick. A second bobbin of the yarn was takendirectly from the machine and in the acid state was cut to 4- inohstaples. These staples (still straight after cutting due to inhibitingaction of the NaaSOr) were dropped intowater and crinkiing took placeimmediately and spontaneously, resulting in a crinkled chip only inch inlength. In this case, rate of crinkling was very fast and was completealmost the instant the yarn touched the water. When dried yarn above iswet in dimethyl dlbenzyl ammonium hydroxide, the rate is somewhat slowerdue to slower penetration of water into the interior of filament andcurling of filaments may be seen to take place over a period of a fewseconds. If the washed yarn is cut from bobbin before drying, crinklingtakes place at the instant of cutting but gives hardly as fine crinkleas when complete and instantaneous shrinkage is permitted by droppingthe acid staple into a large volume of water.

Example V Viscose with a composition of 13% each of cellulose andcaustic soda was spun at a salt index of 5.0 into an acid bath with thecomposition 150 g./liter H2804, 330 g./1lter NazsOi, l5 g./liter ZnSOiand 50 g./liter glucose maintained at 50 C. using a spinneret with 120holes. The filaments of 275 total denier were pulled through the spinbath for inches at a speed of 80 m./mm., stretched 20% betweenpositively driven rollers, passed through water at 80 (3., stretched anadditional cut into staples and dropped into water; crinkling occurringimmediately and spontaneously. The resultant fiber was highly crinkled,had dull lustre and good hand.

By the process 01' the invention in its various modifications, filamentshave been produced which show a wide variety of three-dimensionalcrinkle, both in filament yarn and in staple. The process isparticularly adapted to spinning of wool-like staple fiber havingfilament deniers of 1-7 or even lower. The ability to spin crinkledfilaments of such fine denier is particularly notable, Yarn of, forexample, 2 denier per filament is exceptionally soft, has an exceedinglylarge number of crinkles per inch and has very good tensile properties.Tensile tests on single staple fiber show tenacities of greater than 3g./denier dry with elongations of about 20% in the fiber itself notconsidering the elongation due to crinkle. The elongation due to crinklein these staples is often greater than 100%.

From the preceding results and characteristics, it appears that thetendency to crinkle is an inherent characteristic of the filaments ofthe invention after having once been stretched and that the crinkledform represents the normal equilibrium state. When straight yarnproduced by spinning under high tension followed by washing and dryingunder tension is treated with water while free to shrink, it is usuallyfound that the crinkling incurred is somewhat less than the 8 degree ofcrinkling. It has, however, been found that with this dried yarn,certain solutions such as a 50% aqueous solution of potassium iodide, a1% solution of NaOH, or a 5% solution of dimethyl dibenzyl ammoniumhydroxide return the yarn to a highly swollen gel state and give bettercrinkling than does water alone: no better, however, than is originallyobtained if crinkllng has been induced with water before the yarn hasbeen dried at all.

Filaments which have been subjected to high tension during spinning maybe preserved in the straight state if they are given a washing treatmentwith a substantially saturated solution of ammonium sulfate. Theammonium sulfate treated filaments are not subject to markeddeterioration and since shrinkage is inhibited by the ammonium sulfatesolution the filaments may be kept in the straight form, then convertedat will into the crinkled form merely by washing with water. Apparently,acid alone over a wide range in concentration has little, if any, effecton crinkling of the filament but will, of course, over a period of timeif left in the filament, exert some degrading influence on the celluloseitself.

The different performance of the above-given examples of ammoniumsulfate and potassium iodide when added in high concentrations to thewash water may possibly be explained by the progressive influence of theanions as exemplified in the well-known Hofmeister series registeringthe order of lyotropic action of ions. In this series the sulfate ion isnear one extreme, whereas the iodide ion is near the other.

An experiment illustrating the permanency oi the crinkles may be carriedout by simply boiling some of the crinkled filaments in water for aperiod of several hours, then drying. Repeated treatments of this shortdo not noticeably impair the crinkles. It is notable that the crinklesare so permanent in the wet state.

When a sample of crinkled filaments is dropped into a caustic sodasolution of about 6% concentration, swelling is great and the crinklesdisappear leaving the filaments essentially straight. If, however, thefilaments are removed from the caustic soda, washed with water free ofcaustic soda, and dried, it is found that the crinkles have beenregained and to a degree comparable to the original. If a caustic sodasolution of 18% concentration is used instead of 6%, the swelling isless and the crinkles do not completely disappear from the filamentswhile immersed in the caustic soda solution.

The crinkled filaments of the invention possess certain characteristicswhich are manifest by the frequency and type of crinkles, thecross-section of the filaments, the orientation, dye absorption, X-raydiffraction, difiraction of polarized light and tensile properties.

The cellulosic products of the invention are especially suitable for usein staple fiber, in continuous filament rayon thread or yarn, and intextile fabrics made in whole or in part therefrom. The crinkledfilaments of the invention, in the form of staple fiber, may be formedinto thread or yarn by the textile operations commonly used in thecotton or the woolen arts without the excessive slippage betweenfilaments which occurs when ordinary rayon staple is spun into thread.In addition to these properties, groups of the filaments, such ascontinuous filament yarns and spun staple fiber, are remarkably soft andbulky. In fine denier filaments, and especially in staple fiber, theproduct of the invention amass? has wool-like properties. The filaments,before or after crinkling, may be formed into threads and yarns ofvarious kinds. The filaments may be crinkled before or after beingtwisted into a thread. The thread, whether crinkled or uncrinkled, maybe spun, woven or knitted into various fabrics or materials. Specialeffects may be obtained by crinkling such fabrics or materials afterthey have been formed. Combinations of the filaments of the inventionmay include threads comprising filaments of the invention intermingledor intertwisted with fibers or threads 01 such materials as linen,cotton, rayon, cellulose acetate, silk, nylon, spun proteins, wool andthe like. The filaments may have been crinkled before or after thecombination or left straight with potential crinkle. The knitted goodsand fabrics oi the invention may be formed in whole or in part of suchcombination threads, or they may be formed with alternate arrangementsgiving novelty eil'ects.

An important advantage of our invention is the providing of a simple,eifective method for spinning crinkled or potentially crinkled viscosefilaments in the conventional single bath commonly used for thestretch-spinning of non-crinkled yarns or non-crinkled staple fiber tow.For example, one type of single bath spinning operation to which theinvention is particularly suited is carried out in conventionalstretch-spinning apparatus wherein are provided rollers, double godetwheels or other mechanical devices common- 1y used to give the yarn ahigh degree of stretch in the production of high tenacity yarn. It is tobe emphasized, however, that in any case the invention provides a methodfor spinning crinkled filaments in a conventional single bath spinningoperation of the type used for high stretch spinning, but in any casewithout requiring any mechanical alterations from the apparatus normallyused for spinning straight filaments.

Another advantage of our invention is the provision of an extremelyflexible method for changin: all or a portion of a viscose rayonoperation back and forth between production of crinkled and straightfilaments. The spinning process of the invention uses without anychanges in composition whatsoever, the same normal "Muller spin bathscommonly used in the production of straight filaments by the viscoseprocess. With the process of the invention. the same circulating spinbath system may be used to supply difi'erent sets of spinning frames,simultaneously producing both crinkled and straight filaments.

We claim:

1. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose into a "normal Muller spin bath free fromappreciable quantities of iron and containing per liter 125 to 150 gramsH2804, 235 to 330 grams NazSOi and 12 to 15 grams ZnSOi to formcoagulated and regenerated cellulose filaments, subjecting the filamentsto high tension stretching during coagulation and regeneration, washingand drying the filaments without appreciable shrinkage, whereby thedried filaments develop the potential capacity to crinkle spontaneouslywhen treated with water.

2. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose solution into a. "normal Muller spin bathfree from appreciable quantities of iron and containing per liter tograms H2804, 235 to 330 grams Na2S0i and 12 to 15 grams 211804 to formcoagulated and regenerated cellulose filaments, subjecting the filamentsto stretching under a tension of more than 0.5 gram per denier duringcoagulation and regeneration, whereby the stretched, regeneratedfilaments develop the capacity to form spontaneously on wetting withwater a multiplicity of fine crinkles.

3. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being around 1and the salt index from 4.0 to 7.5, extruding the viscose solution intoa normal Muller spin bath" free from appreciable quantities of iron andcontaining per liter 125 to 150 grams H2804. 235 to 330 grams NMSOi and12 to 15 grams ZnSOr to form coagulated and regenerated cellulosefilaments, and stretching the filaments during coagulation andregeneration under high tension of more than 0.5 gram per denier but notso high as to cause appreciable breakage of the filaments.

4. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose solution into a "normal Muller spin bath"free from appreciable quantities of iron in which sulfuric acid andsodium sulfate are present in such proportions that the bath consistssubstantially of a solution of NaHSOs together with some excess NaaSOito form coagulated and regenerated cellulose filaments, duringcoagulation and regeneration stretching the filaments under hightension, washing and drying the filaments without appreciable shrinkage,and at any time thereafter treating the dried filaments with watercontaining a swelling agent and permitting them to shrink freely and tocrinkle.

5. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose solution into a "normal Muller spin bath"free from appreciable quantities of iron in which sulfuric acid andsodium sulfate are present in such proportions that the bath consistssubstantially of a solution of NaHSOq together with some excess NaaSOcto form cellulose filaments, during coagulation and regenerationsubjecting the filaments to stretching under a spinning tension of atleast 0.5 gram per denier, and crinkling the stretched cellulose whilewet with water and under conditions permitting free shrinkage.

6. The improvement in the viscose process which comprises forming aviscose solution having from 9% to 13% of cellulose and from 8% to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose solution into a "normal Muller spin batfree from appreciable quantities of iron and containing per liter 125 to150 grams H2804, 235 to 330 grams NaaSOi and 12 to 15 grams ZnSOr andduring regeneration stretching the resulting filaments under hightension, remov- 11 ing the regenerating medium which inhibits crinkling,and while the filaments are wet permitting them to shrink freely and tocrinkle.

7. The improvement in the viscose process which comprises forming aviscose solution containing from 9% to 13% of cellulose and from 8% to13% of caustic soda, the ratio of cellulose to caustic soda being from0.833 to 1.13, extruding the viscose solution into a normal Muller spinbath" free from appreciable quantities of iron in which sulfuric acidand sodium sulfate are present in such proportions that the bathconsists substantially oi a solution of NaHsOi together with some excessNazSOr to form coagulated and regenerated cellulose filaments, duringcoagulation and regeneration stretching the filaments under hightension, washing and drying the stretched filaments without appreciableshrinkage, and treating the filaments with water having a compounddissolved therein which has a lyotropic action that enhances swellingand thereby crlnkling the filaments.

8. The improvement in the viscose process which comprises forming aviscose solution containing from 9% to 13% of cellulose and from to 13%of caustic soda, the ratio of cellulose to caustic soda being from 0.833to 1.13, extruding the viscose solution into a "normal Muller spin bath"free from appreciable quantities of iron in which sulfuric acid andsodium sulfate are present in such proportions that the bath consistssubstantially of NaHSOi together with some excess NazSO; to formcoagulated and regenerated cellulose filaments, during coagulation andregeneration stretching the filaments under high tension, washing thefreshly spun filaments with a concentrated aqueous solution to removethe acid, said solution containing a salt having a lyotropic action thatreduces swelling and prevents free shrinkage of the filaments.

9. The improvement in the viscose process which comprises forming aviscose solution having about 10% each of cellulose and caustic soda,extruding the viscose solution into a normal Muller spin bath ties ofiron and containing per liter 125 to 150 grams H2804, 235 to 330 gramsNMSOi and 12 to 15 grams ZnSOr to form cellulose filaments, coagulating,regenerating and stretching the filaments under high tension, wherebysaid stretched filaments acquire the potential capacity to crinklespontaneously when treated with water.

10. The improvement in the viscose process which comprises forming aviscose solution having about 10% each of cellulose and caustic soda,extruding the viscose solution into a "normal Muller spin bath" freefrom appreciable quantities of iron in which sulfuric acid and sodiumsulfate are present in such proportions that the bath consistssubstantially of a solution of NaHSOi together with some excess NazSOrto form coagulated and regenerated cellulose filaments, and duringcoagulation and regeneration subjecting the filaments to a tension ofmore than 0.5 gram per denier and without causing an objectionablebreakage of filaments.

11. The improvement in the viscose process which comprises forming aviscose solution having about 10% each of cellulose and caustic soda anda salt index of 5.5 to 6.0, extruding th viscose solution into a "normalMuller spin bath" free from appreciable quantities or iron in whichsulfuric acid and sodium sulfate are present in such proportions thatthe bath consists substantially or a solution oi NaHSOi together withsome free from appreciable quantiexcess Nazsoi to form coagulated andregenerated cellulose filaments, and during coagulation and regenerationsubjecting the filaments to high tension stretching under a tension ofmore than 0.5 gram per denier.

12. The improvement in the viscose process which comprises forming aviscose solution having about 10% each of cellulose and caustic soda,extruding the viscose solution into a normal Muller spin bath" tree fromappreciable quantities of iron in which sulfuric acid and sodium sulfateare present in such proportions that the bath consists substantially ofa solution or NaHSO4 together with some excess NazSOc to form cellulosefilaments, coagulating, regenerating and stretching the filaments undera tension of around 1 gram per denier, and while the stretched filamentsare wet with water permitting them to shrink freely and to crinkle.

13. The improvement in the viscose process which comprises forming aviscose solution having about 10% of cellulose, and caustic soda in suchamount with respect to the cellulose that the ratio of cellulose tocaustic soda is from 0.833 to 1.13, extruding the viscose solution intoa "normal Muller spin bath" free from appreciable quantities of iron inwhich sulfuric acid and sodium sulfate are present in such proportionsthat the bath consists substantially of a solution of NaHSO; togetherwith some excess Naisoi to form coagulated and regenerated filaments,during coagulation and regeneration sub jecting the resulting filamentsto high tension stretching, cutting the filaments into staple fiber, andcrinkling the cut filaments while shrinking.

14. The improvement in the viscose process which comprises forming asolution having about 10% each of cellulose and caustic soda, formingrayon filaments not exceeding 2 denier per filament by extruding theviscose solution into a "normal Muller spin bath free from appreciablequantities of iron and containing per liter about to grams H2804, 235 to330 grams NazSOi and 12 to 15 grams ZnSOi, during coagulation andregeneration subjecting the filaments to a spinning tension of more than0.5 gram per denier, and forming a multiplicity of fine crinkles in thefilaments while the filaments are free to shrink.

15. The improvement in the viscose process which comprises forming aviscose solution having cellulose and soda contents within the rangedefined by a pentagon bounded by the following points located on anordinate diagram:

9% cellulose, 8% caustic soda 9% cellulose, 10.8% caustic soda 10%cellulose, 12.0% caustic soda 13% cellulose. 13% caustic soda 10%cellulose, 8.9% caustic soda to crinkle spontaneously when wet withwater under conditions permitting free shrinkage.

PAUL HENRY SCHLOSSER. REID LOGAN MITCHELL.

(References on iollowinl page) 13 14 REFERENCES CITED FOREIGN PATENTSThe following references are of record in the Number Country Date fileof this patent: 353,483 Germany May 18, 1922 386,133 Germany Dec. 3,1923 UNITED STATES PATENTS 5 490,961 Germany Feb. 14, 1930 492,279Germany Sept. 18, 1930 Number Name Date ,214,931 Leduc Feb. 6, 1917703537 France Feb 1931 1,260,508 Borzykowskl Mar. 26, 1918 705-917France 1931 1,881,740 Lilienfeld Oct. 11,- 1932 u OTHER REFERENCES a?3LT Suvern: Die Kunstliche Seide, published by Julius Springer, Berlin,1926, pages 488-489.

Copy in Division 15.

